Industry has for many years utilized techniques for cutting and polishing materials such as glass, metals, semiconductors, stones, crystals, and the like. In general, the processes include one or more polishing steps in which a polishing pad of a suitable material is applied against the surface to be treated with motion and pressure. A mechanical and/or chemical polishing formulation, usually in slurry form, can be located between the pad and the surface to be treated. When pressure is applied, the polishing formulation carried in the slurry can cut, grind, and/or polish the surface, finishing the surface to the desired topography.
Over time, it has become necessary to develop methods for cutting and polishing substrate surfaces to ever decreasing levels of surface variation from planar. For example, maximum surface variations from planar on the order of angstroms are now desirable when forming products such as semi-conductor wafers and computer hard discs. As such, improvements to chemical mechanical polishing processes have been developed in an attempt to meet the desired standards. For example, slurry delivery and distribution across the face of the polishing pad has been improved through the development of flow channels, holes, or pressure variations across the pad itself such as described in U.S. Pat. Nos. 5,489,233 to Cook, et al., 5,533,923 to Shamoiullian, et al., and 5,562,530, to Runnels, et al., all of which are incorporated herein by reference. Other methods developed to improve polishing techniques have evolved around improvements to the pad material itself, such as those methods described in U.S. Pat. No. 6,126,532 to Sevilla, et al., also incorporated herein by reference that describes an improved open-celled, porous polishing pad substrate having sintered particles of synthetic resin.
Unfortunately, in spite of such improvements, problems can still arise at any point in the polishing process, preventing the formation of a surface having the desired planar surface. For instance, any of the polishing pads used in a multi-stage polishing process, from the initial lapping process to the final chemical mechanical polishing process, can develop uneven surface abnormalities, which can transfer to the substrate being polished.
For example, FIG. 1 illustrates a typical prior art polishing pad system generally 10 including an uppermost polishing pad 12, carrying a layer of a polishing slurry 25. The polishing pad system 10 also includes an adhesive laminate 15 that includes a first adhesive layer 14, a second adhesive layer 16, and an impermeable film layer 18 between the two. The polishing pad system 10 can be attached to a platen 20 via the adhesive laminate 15, as shown. As can be seen in FIG. 2, during the polishing process, gas micro-bubbles 8 can form in the adhesive layers 14, 16. During the course of operating the system, the micro-bubbles 8 can agglomerate and form larger bubbles 13. The larger bubbles 13 can exert pressure on their surroundings, and in particular on the impermeable layer 18 adjacent the adhesive layer 16. This pressure can in turn cause a deformity 22a to develop in the impermeable layer, as can be seen in FIG. 2. This deformity 22a can translate upward through the other layers of the system, and can cause a similar deformity 22b to develop on the polishing surface of the polishing pad 12. Once a polishing pad becomes uneven at its surface, as illustrated in FIG. 2, its useful life is over as a surface deformity 22b can be transferred from the pad to the surface of the substrate to be polished, and the substrate itself can be rendered useless for its intended purpose or even destroyed.
A need currently exists for an improved polishing system. In particular, what is needed in the art is a polishing system that can prevent surface deformities from developing on the polishing surface of the system.